Compressor



Nov.` 6, 1951 A E M11-@HELL 2,573,863

COMPRESSOR Filed May 19, i948 v Y s sheets-sheet 1 n ,47 a TE 4mv/ l5 2o lb n j 30 'v5-, ,3| 32 33 i 4l 34- ,27

x f :ill- :TI/ E 4o 2 2 al l| 45 i 3o W5 my ATTORNEY A. E. MITCHELL COMPRESSOR Nov. 6, 1951 5 Sheets-Shee'l 2 Filed May 19, 1948 ATTORNEY.

NOV. 6, 1951 A, -E MITCHELL 2,573,863

COMPRESSOR Filed May 19, 1948 :s sheets-sheet :5

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Patented Nov. 6, 1951 UNITED STATES PATENT OFFICE.

COMPRESSOR Alva E. Mitchell, Philadelphia, Pa.

Application May 19, 1948, Serial No. 27,892

Claims. l

This invention relates to compressors.

It is the principal object of the present invention to provide an improved positive displacement compressor capable of construction by mass production methods, and which will be compact `and light in weight.

It is a further object of the present invention to provide a compressor With unloaded starting.

It is a further object of the present invention toprovide a compressor havingvariable capacity, with automatic stroke regulation for modifying the capacity.

It is a further object of the present invention to provide a compressor having improved provisions for controlling the capacity thereof directly from a controlling element.

It is a further object .of the present invention to provide a compressor which is inherently balanced and capable of smooth and quiet operation at relatively high speeds.

It is a further object of the present invention to provide a compressor having a simplied form of actuation of the compressor pistons.

Other objects and advantageous features of the invention Will be apparent from the specication and claims.

The nature and characteristic features of the invention will be more readily understood from the following description, taken in connection with the accompanying drawings forming part hereof, in which:

Figure 1 is a, longitudinal sectional view of a compressor in accordance with the present invention, the valve plate being rotated to show the position of the suction and discharge ports in relation to the cylinders;

Fig. 2 is a transverse sectional view taken approximately on the line 2-2 of Fig. 1;

Fig. 3 is a fragmentary sectional view taken approximately on the line 3-3 of Fig. 2;

Fig. 4 is a transverse sectional view taken approximately on the line 4-4 of Fig. l;

Fig. 5 is a longitudinal sectional view of a compressor in accordance with the present invention showing one arrangement of automatic unloader and stroke regulator and with the valve plate as seen along the line 5-5 of Fig. 6;

Fig. 6 is a transverse sectional view taken approximately on the line i-B of Fig. 5;

Fig. '7 is a transverse sectional view taken approximately on the line 'l-l of Fig. 5;

Fig. 8` is a longitudinal sectional view of a compressor in accordance with the present invention showing another arrangement of automatic unloader and stroke regulator;

Fig. 9 is a fragmentary view in elevation illustrating the details of the trunnion pins;

Fig. 10 is a fragmentary sectional view taken approximately on the line i-l of Fig. 8, and with the angle plate revolved to the no-load position;

Fig. l1 is a fragmentary transverse sectional view taken approximately on the line ll-H of Fig. 8; and

Fig. 12 is a fragmentary sectional view taken approximately on `the line iZ-IZ of Fig. 8 Aand illustrating the provisions for longitudinal adjustment of the thrust bearing.

It should, 'of course, be understood that the description and drawings herein are illustrative merely. and that various modcations and changes may be made in the structure disclosed without departing from the spirit of the invention.

Like numerals refer to like parts throughout the several views.

Referring noW more particularly to the drawings, the compressor in accordance With the present invention preferably includes an exterior cylindrical casing l5 closed at one end by an end closure plate I6, the closure plate I6 preferably being secured in position With respect to the ,casing I5 such as by longitudinally disposed studs Il, as indicated in Figs. 1 and V5. At the opposite end of the casing l5, a valve plate i8 is provided, in xed relation to the casing l5. The valve plate I8 is preferably provided with 'a suction or inlet port I9 having the inner end thereof longitudinally disposed, and with a delivery or discharge port 20 also having the inner end thereof longitudinally disposed. The valve plate I8 is provided With a suitable bearing 2| and a drive shaft 22 is provided Which extends centrally through the Valve plate I8 and the bearing 2l therein and is journaled at its inner end in a bearing 23 carried by the end plate I6. A seal 24 may be provided, removably mounted in the valve plate I8 for preventing fluid leakage along the shaft 22.

Within the casing l5, a cylindrical bearing or Wear sleeve 25 may be provided, and, Within the sleeve` 25, a rotor 26 is carried, the rotor 26 being fixedly mounted with respect to the shaft 22 for rotation therewith. The rotor 26 is provided with a plurality of axially extending bores 21, which serve as Working cylinders Within the rotor 2S, the ends 28 of the bores 21 adjacent the valve plate I 8 preferably being tapered and provided with a small cylindrical terminal 23, for communication, as hereinafter explained, with the inlet port I9 and with the discharge port 20.

Packing rings 36 may be interposed lbetween the valve 'plate I8 and the rotor 26 for preventing iiuid leakage. y Within each of the cylinders provided by the bores 21 a piston 3| is mounted for axial reciprocation therein in parallel relation with the shaft 22. Each of the pistons 3|, adjacent the valve plate I8 has an end portion 32 complemental to the ends 2 8 of the bores 21 and may also have a cylindrical terminal S3 filling the space provided by the bore terminal 29 for reducing the clearance volume in the cylinder to a minimum.

Each of the pistons 3| preferably has a connecting rod 34 pivotally connected thereto. The connecting rods 34 are pivotally connected at their opposite ends to bearing rings 35. The bearing rings 35 are supported by bearings shown at 36 in Fig. 1, at 31 in Fig. 5 and at 88 in Figs. 8 and l0, in a cap ring 49. The cap ring 48 may be mounted on trunnions 4| at each side thereof, as illustrated in Fig. 4, or on a plurality of trunnions 42 and 43, as illustrated in Figs. 8 and 10.

The pivotal axis of the cap ring 46, provided by the trunnions 4| or 42 and 43, is located so as to be conicident with the path of the lower end of each connecting rod 34 as each piston passes through the point of top dead-center, so that the top dead-center is xed regardless of the positioning of the cap ring 49. The cap ring 49 is provided with a pair of curved lugs 45 which are adapted for engagement by transversely movable cam elements 46.

The cam elements 46, as indicated in Figs. 1, 2 and 3, may be mounted for transverse movement with respect to a cam mounting plate 41 carried within the housing I5, the cam elements 46 having guide portions 48 for engagement, in parallel slots 49, having limit stops 49a, in the cam mounting plate 4l. Transversely disposed springs 59 may be provided in spring sockets 5I and interposed between the cam elements 46 and longitudinally extending portions 52 of the cam mounting plate 41 for normally urging the cam elements 46 into engagement with the lugs 45 and to a position for unloading with minimum piston stroke.

Referringnow more particularly to Figs. 5, 6 and '7 of the drawings, the rotor sleeve 25 is provided with an oil delivery slot 55 which communicates with a groove 55 on the inner face of the valve plate I8, oil passageways 51 being provided in communication with the face of the valve plate I8 and with the bearing 2| in the valve plate I8.

The valve plate I8 may also be provided with a relief valve plate 66 axially movable in the valve plate I6 and normally impelled by springs 6I into seated position for preventing damage from slugging In place of the springs 59 shown in Figs. l and 2, the casing I may be provided, as illustrated in Figs. 5 and '1 with an outwardly extending tubular housing 65, closed at its outer end by an end closure cap 66, having an internally threaded portion 61 in engagement with the threaded exterior of the housing 65, for adjustment.

A sealing bellows 68 is provided, connected at one end to the closure cap 66 in uid tight relationship and connected at the other end in fluid tight relationship to an actuator plate 69. The interior of the bellows 68 is preferably vented to the atmosphere through a restricted port 19 in a cap plug 1I mounted in the closure cap 66, and the exterior of the bellows 68 is in communication with the interior of the casing I5 through a port 11, preferably restricted. Within the interior of the bellows 68 the unloading spring 56a is provided. The actuator plate 69 is preferably provided with an internally threaded boss 'I2 for attachment, if desired, of an actuating rod (not shown) for actuation by any desired actuator, the plug 1I being removed for this purpose.

The cam elements 46 may be guided in their transverse movement by a guide sleeve 13 movable in the housing 65, and adjustable limit stops 49h may be provided in the casing I5.

Referring now more particularly to Figs. 8 to l2, inclusive, a double pivoted mounting may be provided for the cap ring 40 which includes the trunnion pins 42 and 43 carried by an end wall plate 89 mounted in a sleeve 8| in the casing I5. The pins 42 are mounted in blocks 82 slidable in arcuate guide ways 83 in the sleeve 8| and the pins 43 are mounted in blocks 18 slidable in guide ways 84, also mounted in the sleeve 8|.

The bearing 23 may also be mounted in the end wall plate 89 and adjusted endwise to adjust the rotor clearance by means of studs 19. The end wall plate 36 and the sleeve 8| are held in position by radially disposed studs 85. An end closure plate 86 may be mounted outside the end wall plate 89. The end wall plate 89 may be provided with parallel guide slots 49.

Interposed between the plate 89 and the cam elements 45 a pair of ilexible metallic bellows 81 may be provided, closed at their lower ends by an actuator plate 88 in engagement with the cam elements 46 and closed at their upper ends by abutment plates 89 in abutting relation to the plate 80. The plate 89 is provided with a fluid passageway 90 in communication with the interiors of the bellows 81 through restricted openings 9! in the abutment plates 89 and may be connected by a fluid connection 92 to a pilot cylinder 94. The pilot cylinder 94 has mounted therein an adjustable head 93 and a pilot piston plate 95, to which one end of a flexible metallic bellows 95 is secured in iiuid tight relationship. rlhe other end of the bellows 96 is secured in uid tight relationshipjto an abutment plate 91. A compression spring 98 is provided, interposed between the Icylinder head 93 and the piston plate 95. A plug 99, having a restricted opening |99 therein may be provided for closing the end of the cylinder 94. The piston plate 95 may be provided with a threaded boss IBI for engagement by an actuator rod (not shown) upon removal of the plug 99.

The cylinder 94 may be placed at any desired location and the system which includes the bellows 95, the fluid connection 92, and the bellows 81 may be lled with fluid, compressible or inc'ompressible, as desired.

The fluid connection 92 may also be vprovided with a three-way valve |62 in communication with a fluid conduit |63 for connection to any preferred source of pressure for direct fluid pressure operation, if desired, of 'the bellows 81.

The mode of operation will now be pointed out.

It will be noted that the stroke of the pistons 3|, upon rotation of the rotor 26, is determined by thepositoning of the cap ring 40. When the cap ring 48 is substantially perpendicular to the shaft 22, so that the cam elements engage the limit stops 49a or 49h, a very short stroke of the pistons 3| is available and as the cap ring 49 is shifted angularly the stroke of the piston 3| is increased, with increase of load or as determined 5` by the force applied on the cam elements 46, as hereinafter more fully explained.

When the compressor is at rest the springs '56 in Figs. l and 2, the springs 5l]ab in Figs. 5 and 7, or the bellows 8l in Figs. 8 and 11 are normally expanded so that the cam elements l5 are moved downwardly to a position to shift the cap ring i0 to provide a minimum stroke.

Upon rotation of the shaft 22, and 'the rotor 26 carried thereby, the terminal ends 29 of the bores 2l are successively advanced past the inlet port IS in the valve plate I8 and the delivery or discharge port 2B in the valve plate I8. The pistons 3l are positioned by the cap ring v4&3 so that they are at the rod ends of their strokes as each cylinder bore 2l moves beyond the end of the inlet port I9 and Yat the head or valve plate end of their strokes as they move beyond the end of the delivery port 2G.

Fluid in the bores 2 as the successively advance between the ports I'S and 2E! is compressed in the working chambers in the bores 2l.

Referring now to Figs, 1 to 4, inclusive, the compressor is unloaded at starting. As the pressure in the working spaces increases, the force therefrom is effective through the piston rods v36 against the cap ring 4G and therefrom through the lugs 115 against the cam elements 45 and therefrom against the force exerted by the springs 5f) until and during operation at full stroke. When the compressor stops the pressure is equalized between the inlet and the outlet and the springs 5B return the cam 136 toits unloaded position.

The use of a rotor and valve plate permits of high speed operation and the reduction of clearance in the bores 2l reduces re-expansion losses.

-Referring now more particularly to Figs. 5, 6 and '7, in the form of compressor there shown provision is made-for unloading at starting and il the compressor also adjusts itself to the `load within the limits of its capacity. The capacity adjustment is gradual or modulated by reason of the action of the spring 58a, the cam 65, and

by the spring action of the bellows 68, and the restriction l@ provides a dash pct effect with the spring 5E!a separated and the remainder of the compressor sealed therefrom. The spring 59a may also be adjusted by turning the cap 65.

An equalizer connection 'l is provided in communication with the suction line so that the inlet pressure is effective within the interior of the casing l5. f l

If desired, the plug 'il may be removed and the desired force application made through the boss 'l2 by any desired metering device (not shown), temperature, humidity or otherwise responsive, as preferred.

Lubrication is provided through the slot 55, grooves 5E and passageways 5l.

If the pressure should become excessive the relief valves 66 are available for by-passing fluid to the delivery port 2G.

Referring now more particularly to Figs. 8 to l2, inclusive, the unloading spring 98 is eXteriorly disposed with respect to the casing I5. The interior of the bellows 8l and 95 and the fluid. connection therebetween may be filled with liquid, or with gas under pressure, to provide a fluid link between the bellows @l and the bellows @t and with the restriction |09 acting in a manner similar to restriction 10. If desired also, the

plug iig may .be removed and an actuator (not shown) connected to the boss il!! for control from a metering element (not shown).

VIf pressure fluid application against the bellows 8l Afrom an exterior source of uid under pressure iss-desired, the valve H32 may be positioned for access of -fiuid through the fluid connection |93 in-either direction.

In the compressor as illustrated in Figs. 5 to 12, inclusive, the inlet pressure may be varied, as desired, over a wide range from sub-atmospheric pressure to pressures of the order of fifty pounds. The inlet pressure is effective through the equalizing yconnection 16 and in opposition to that effective in the interior of the bellows 68 or the bellows 8l.

I claim:

1. In a compressor, a tubular casing, a valve plate in said casing and having an interior face with fluid inlet and fluid delivery ports therein, a rotor in said casing in facing relation to said valve plate and having a plurality of longitudinal bores for respective register with said ports, pistons reciprocable in said bores, a ring member, piston rods connected to said ring member and to said pistons, pivotal mounting means for said ring member the pivotal axis of which is coincident `with the pivot of one of said piston rods at said ring member for one dead center position of said one of said piston rods, an abutment member on said mounting means, a transversely movable cam member in said casing for positioning said ring member and resilient means for impelling said cam member.

2. In a compressor, a tubular casing, a valve plate in said casing and having an interior face with fluid inlet and fluid delivery ports therein, a rotor in said casing in facing relation to said valve plate and having a plurality of longitudinal bores for respective register with said passageways, pistons reciprocable in said bores, a ring member, piston rods pivotally connected to said ring member and to said pistons, pivotal mounting means for said ring member the pivotal axis of which is coincident with the pivot of one of said piston rods at said ring member for one dead center position of said one of said pistons, an abutment on said mounting means, a transversely movable cam member having an angularly disposed face for engagement with said abutment for positioning said ring, and resilient means for impelling said cam member for varying the stroke of the pistons.

3. In a compressor, a tubular casing, a valve plate closing one end of said casing and having an interior face with fluid inlet and fluid delivery ports therein, a closure member at the other end of said casing, a longitudinally extending shaft in said casing, a rotor on said shaft in facing relation to the interior face of said valve plate and having a pluraliti7 of longitudinally disposed cylinder bores for respective register with said ports, pistons reciprocable in said bores to and from said valve plate, a ring member, piston rods pivotally connected to said ring member and to said pistons, pivotal mounting means for said ring member, an abutment member on said mounting means, a transversely movable cam member mounted on said closure member and having an angularly disposed face for engagement with said abutment for positioning said.

ring, and resilient means for impelling said cam member. v

4. In a compressor, a tubular casing, a valve plate in said casing having an interior face with arcuately disposed fluid inlet and fluid delivery ports therein, a rotor in said casing in facing relation to the interior face of said valve plate and having a plurality of longitudinal bores for respective register with said ports, circularly disposed luid sealing members interposed between said valve plate and said rotor, pistons reciprocable in said bores, a ring member, piston rods pivotally connected to said ring member and to said pistons, pivotal mounting means for said ring member, an abutment on said mounting means, a movable cam member having an angularly disposed face for engagement with said abutment for positioning said ring, and means for impelling said cam member.

5. A compressor as defined in claim 1 in which the pivotal mounting means comprises pins carried by the casing.

6, A compressor as defined in claim l in which the pivotal mounting means comprises alined pins journaled in the'casing and providing a pivotal axis oiset from the axis of the rotor.

7. A compressor as defined in claim 1 in which the pivotal mounting means includes trunnions at the pivotal axis and pivots having their axes intersecting and normal to the axis of rotation of the rotor.

8. A compressor as dei-ined in claim 1 in which the pivotal mounting means includes trunnions at the pivotal axis mounted in arcuate guideways and pivots having their axis intersecting and normal to the axes of rotation of the rotor mounted in longitudinally extending guideways.

9. A compressor as dened in claim 1 in which the iluid delivery port has in communication therewith a resiliently impelled relief valve for the delivery of excess fluid in the bores to said delivery port.

l0. A compressor as dened in claim 1 in which the uid delivery port includes a passageway having interposed therein a resiliently impelled relief valve for the delivery of excess fluid in the bores to said delivery port.

1l. A compressor as dened in claim 1 in which a rotor enclosing sleeve is mounted in the casing passageways in communication with the facing portions of the valve plate and the rotor.

12. A compressor as dened in claim 1 in which the resilient impelling means includes a Iluid pressure responsive member in actuating relation to said cam member and uid connections in communication with said pressure responsive member for applying fluid pressure thereagainst.

13. A compressor as defined in claim 1 in which a fluid connection is provided in communication with the interior of the casing and with the fluid inlet connectionl and in which the resilient impelling means includes a fluid pressure responsive member against which the pressure in the interior of the casing is effective.

14. A compessor as defined in claim l in which a fluid connection is provided in communication with the interior of the casing and with the fluid inlet connection, and in which the resilient impelling means includes a fluid pressure responsive member against which the pressure in the in-l terior of the casing is effective, and variable means for applying a pressure against said fluid pressure responsive member in opposition to the interior pressure.

15. A compressor as dened in claim l in which the resilient impelling means includes a uid pressure responsive member in actuating relation to said cam member, a second fluid pressure responsive member, fluid connections between said pressure responsive members, and a resilient loading member in engagement with said second pressure responsive member.

ALVA E. LUTCHEIL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 978,668 Slick Dec. 13, 1910 2,148,277 Rose Feb. 2l, 1939 

